1. Field of the Invention
The present invention relates generally to image guided radiotherapy, and in particular, the invention relates to volumetric image guided adaptive radiotherapy.
2. Discussion of the Related Art
Presently, online treatment dose construction and estimation include portal ex-dose reconstruction to reconstruct treatment dose on a conventional linear accelerator. Specifically, the exit dose is measured using an MV portal imager to estimate treatment dose in the patient. However, this method has not been employed for patient treatment dose construction, since the dose reconstruction method lacks patient anatomic information during the treatment, and the scattered exit dose is difficult to calibrate properly.
In the past, a single pre-treatment computed tomography scan has been used to design a patient treatment plan for radiotherapy. Use of such a single pre-treatment scan can lead to a large planning target margin and uncertainty in normal tissue dose due to patient variations, such as organ movement, shrinkage and deformation, that can occur from the start of a treatment session to the end of the treatment session.